Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show that he acted in conformity therewith. It may, however, be admissible for other purposes such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident.

So, let's say that a defendant is charged with armed robbery. And let's say that when the defendant was arrested for this crime, a "green leafy substance" was recovered from his vehicle. Is evidence of this substance admissible to prove his motive for committing the robbery. Let's take a look at the recent opinion of the Court of Appeals of Mississippi in State v. Smith, 2012 WL 613324 (Miss.App. 2012).

The facts in Smith were as stated above, with Antonio Smith being convicted of armed robbery based upon a gas station robbery. Before trial, Smith filed a motion in limine, arguing that evidence of the green leafy substance was inadmissible under Mississippi Rule of Evidence 404(b) to prove motive. In response, however,

The trial judge apparently misinterpreted the nature of the 404(b) issue. Instead, he seemed primarily concerned about the substance being authenticated as marijuana. He deferred ruling on the admissibility of the evidence, instructing:

[T]he defendant states that there is indication that witnesses may say the defendant was in possession of marijuana. The court finds that that will not be admissible unless there is someone that will give testimony that the substance was indeed marijuana that was found in the automobile. Otherwise, it would be hearsay and it would not be admissible unless the substance was indeed tested and determined to be marijuana.

After the prosecution later presented testimony authenticating the green leafy substance as marijuana, the trial court allowed for admission of the subject evidence.

After he was convicted, Smith appealed, and the Court of Appeals of Mississippi correctly noted that the trial court incorrectly skirted the Rule 404(b) issue. And the court then agreed with Smith that the subject evidence was inadmissible to prove motive because "[t]he State presented no evidence that Smith robbed the gas station for money to purchase drugs, nor did it even mention this purported motive to the jury during closing arguments."

That said, the appellate court deemed the trial court's error in admitting the marijuana evidence to be harmless given the other evidence of Smith's guilt and affirmed his conviction.